27599 2014-12-12 22:32:46 +0000 Allow SourceBuffer.trackDefaults to be nullable 2015-01-09 19:28:41 +0000 1 1 1 Unclassified HTML WG Media Source Extensions unspecified PC All RESOLVED FIXED P2 normal CR 1 wolenetz acolwell acolwell b.gajda mike philipj public-html-media public-html-bugzilla oldest_to_newest 116239 0 wolenetz 2014-12-12 22:32:46 +0000 In current spec, if an app wants to clear a SourceBuffer's non-empty trackDefaults, it must set the attribute to a TrackDefaultList that was constructed with an empty sequence<TrackDefault>. For example: ... sb = mediaSource.activeSourceBuffers[0]; sb.trackDefaults = new TrackDefaultList( [] ); ... This bug is to request change to spec to make this operation more natural, by specifying: 0. the SourceBuffer.trackDefaults attribute is nullable 1. the SourceBuffer.trackDefaults attribute setter allows null 2. the initial value of SourceBuffer.trackDefaults is null 3. the default {language, kind, label} algorithms behave correctly if trackDefaults is null These changes would be app-visible and #2 would possibly break existing apps. Alternatively, maybe #2 should be: 2. prior to any explicit set operation by app, the SourceBuffer.trackDefaults attribute getter should return an empty TrackDefaultList object that is the same object (===) each time for this SourceBuffer. 116242 1 philipj 2014-12-12 23:40:05 +0000 I think letting it default to null seems the most sane, a dummy object that doesn't hold any real info is a bit odd. 116270 2 philipj 2014-12-13 20:34:32 +0000 About potential breakage, has SourceBuffer.trackDefaults been shipped in any browser? 116397 3 acolwell 2014-12-16 19:40:55 +0000 I'm not sure I agree with this position. It seems annoying to me that application code would always have to check for null AND then check for length > 0 before it could actually use the defaults. Having it always be non-null seems like a good way to avoid at least one of these checks. I agree that requiring the [] is ugly. What if I made the constructor parameter optional and provided a default of []? That at least makes it a little less ugly. 116399 4 wolenetz 2014-12-16 21:14:54 +0000 (In reply to Aaron Colwell from comment #3) > I agree that requiring the [] is ugly. What if I made the constructor > parameter optional and provided a default of []? That at least makes it a > little less ugly. This seems a good approach to me. 116404 5 philipj 2014-12-16 23:17:23 +0000 That seems OK to me too. 116969 6 acolwell 2015-01-09 19:28:41 +0000 Change committed... https://github.com/w3c/media-source/commit/acd9345d853100eea4d5d19eca12347142c857b2